Ignore Hellatze, he doesn't know what he's talking about.
So the Integrity Field Generator makes your ship larger, i.e. easier to hit and easier to run into things? How is that supposed to improve your ship? xD
I thought I read somewhere that the IFG "reduces damage per block by 10". I hope that's 10% and not just a flat "10", because that makes little difference in the post-Iron game, if that's what it does.
To put it simply, it is as you said the first time. Blocks within an integrity field generator will share the damage they take with each other, to a degree.
This is great because now your fragile blocks can utilize some of the durability of your tougher blocks.
This is terrible because instead of just breaking off when destroyed, that block can now cause massive damage to your ship.
I highly advise putting a bumper in front of your ship and not covering it with your IFG.